fix: export table event type from gantt package

[biubiukam]

🤔 This is a ...

• New feature
• Bug fix
• TypeScript definition update
• Bundle size optimization
• Performance optimization
• Enhancement feature
• Refactoring
• Update dependency
• Code style optimization
• Test Case
• Branch merge
• Site / documentation update
• Demo update
• Workflow
• Chore
• Release
• Other (about what?)

🔗 Related issue link

fix #4320

💡 Background and solution

@visactor/vtable-gantt already exposes the nested VTable namespace, but the package entry did not directly export the ListTable TABLE_EVENT_TYPE constants.

This PR re-exports TABLE_EVENT_TYPE from the Gantt package entry and adds a regression test to keep the top-level export aligned with VTable.TABLE_EVENT_TYPE.

📝 Changelog

Language	Changelog
🇺🇸 English	Export ListTable event type constants from @visactor/vtable-gantt.
🇨🇳 Chinese	从 @visactor/vtable-gantt 导出 ListTable 事件类型常量。

☑️ Self-Check before Merge

• Doc is updated/provided or not needed
• Demo is updated/provided or not needed
• TypeScript definition is updated/provided or not needed
• Changelog is provided or not needed

---

🚀 Summary

copilot:summary

🔍 Walkthrough

copilot:walkthrough